Flame retardant brominated styrene-based latices

ABSTRACT

Improved flame retardant polymer latices are disclosed which comprise copolymers of ring-halogenated aromatic monomer units and alkyl acrylate/methacrylate monomer units, and which may additionally include at least one other monomer. In a first embodiment, the latices include ring-brominated aromatic monomer units and alkyl acrylate and/or alkyl methacrylate monomer units. In a second embodiment, the latices include these first two types of monomer units and further include third monomer units from unsaturated esters of saturated carboxylic acids, halogen-free aromatic monomers or unsaturated carboxylic or dicarboxylic acid monomers. In a third embodiment, the latices include four monomer units, namely ring-brominated aromatic monomer units, alkyl acrylate/methacrylate monomer units, halogen-free aromatic monomer units and unsaturated carboxylic or dicarboxylic acid monomer units. In one aspect, the halogenated aromatic monomers are present in an amount to provide from 7 to 20 weight percent bromine in the final latex composition. In another aspect, the halogenated aromatic monomers include polybrominated monomers, particularly to provide monomers having an average of at least about 1.5 bromines per monomer unit. The latex polymers have glass transition temperature in the -30° to 30° C. range for coating, paint adhesive, sealant and non-woven binder applications.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application No. 07/875,740, filed Apr. 29, 1992, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 07/579,063, filed on Sep. 6, 1990, now abandoned, and entitled FLAME RETARDANT BROMINATED STYRENE-BASED LATICES.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the composition and preparation of polymer latices, particularly to such latices including ring-halogenated, ethylenically unsaturated aromatic monomers and at least one other monomer.

2. Description of the Prior Art

Acrylic, styrene-butadiene, styrene-acrylic, vinyl-acrylic, and vinyl acetate VVID latices are commercially used in a variety of surface coatings. In many coatings applications, the latices used are desired to have flame-retarding properties. This applies in particular where latices are used in textiles, carpeting, paints, clear coatings, adhesives, sealants, caulking, non-woven binders and so on.

The usual method by which flame-retardant properties are imparted to latices is the blending-in of flame retardant additives. Many of these flame retardant additives contain bromine, such as brominated diphenyl or diphenyloxide compounds together with antimony trioxide. However, such flame retardant additives have a major disadvantage in that their use gives rise to problems, such as the generation of strong white pigmenting and settling out effect, and toxicity resulting from the presence of antimony trioxide.

A common approach has been the addition of solid organic and inorganic compounds to latices to confer flame retardancy. U.S. Pat. No. 3,887,974 describes the admixture of an aqueous dispersion of a halogenated organic compound and metallic oxide with a polymeric adhesive binder. Although this approach has been shown to provide the desired flame retardancy, many undesirable features are again introduced. Solids ultimately separate from the latex emulsion despite any dispersion techniques employed. The dispersions tend to be high in viscosity and impede application of the latex. Latex films become stiffer due to the presence of solids, interfering with the flexibility or "hand" of the latex. In addition, solids tend to have a pigmenting effect which masks or changes the color of the substrate.

Liquid compounds have been added to latices as well. U.S. Pat. No. 3,766,189 teaches the use of liquid chlorinated paraffin in a latex to achieve fire retardancy. Drawbacks to the use of liquids include migration from the polymer with time, separation from the liquid latex emulsion, adverse effect upon adhesion, plasticizing, swelling of the latex, and poor water resistance. Salts and other water soluble solids eliminate the problems of settling of solids, but contribute other problems cited as well as generally having an adverse effect upon the stability of the latex emulsion.

Chemical integration of monomers into latex polymer to impact flame retardancy has had limited success. Predominantly PVC based latices generally have only a marginal advantage in flammability over non-flame retarded analogs. Addition of more chlorine in the form of vinylidine chloride has been quite limited due to high cost.

Curable resin compositions containing a basic catalyst and a water solution of polymerized halogen-containing vinyl monomer and other vinyl monomers are disclosed in Japanese Patent No. 56120754-A2, issued to Mitsui Toatsu Chemicals on Sep. 22, 1981. The Mitsui patent reports that water based suspensions or emulsions of vinyl polymers have weak resistance to water, cracking and soiling (staining), and that the proposed compositions overcome such short comings. The patent mentions various halogenated vinyl monomers, including brominated monomers, but does not disclose the use of polybrominated monomers.

Moreover, the Mitsui patent is limited to treatment of water, cracking and soiling properties. No recognition is contained in the Mitsui patent of the preparation of flame retardant latices utilizing brominated vinyl monomers, and the patent fails to disclose percentages of use for such monomers to achieve flame retardancy. The patent proposes that the halogen-containing monomer comprise at most 15% by weight of the copolymer, which corresponds to a bromine content in the resin of at most about 6%. The Mitsui patent further indicates that it is preferred to have a lower percentage of halogen-containing monomer of at most 10% by weight, corresponding to a bromine content of at most 4%. These percentages are insufficient to provide desirable flame retardancy. In preferring the lower bromine content, the Mitsui patent teaches away from the present invention.

Bromine-containing plastics are described in European Patent Application No. 70200768.4, filed by Stamicarbon B. V. on Dec. 15, 1979 (published Sep. 7, 1980 as No. 13,052-A1). The Stamicarbon application is directed to the preparation of plastic materials, including polyolefins, polystyrene, and copolymers of styrene and butadiene, styrene and acrylonitrile and ABS. The plastics of the Stamicarbon application require high levels of bromine, and are described as containing 20-44 weight percent of bromine.

Moreover, the polymer compositions in the Stamicarbon patent are not suitable as coating materials because they have inappropriately high glass transition temperature (Tg) values. Their materials would have "excessive stiffness and inability to form film properly at room temperature." In fact, they teach away from the present invention.

Charles R. Martens wrote ("Waterborne Coatings, Emulsion and Water-Soluble Paints", Reinhold, N.Y., 1981, p. 169): "Choice of monomers in emulsion polymerization reactions is largely determined by the end-use requirements of the polymer. The first factor to be taken into account in the choice of a monomer or monomer mixture is the record order or glass transition temperature (Tg) of the polymer desired. This is the characteristic temperature at which the system undergoes a change from a hard, brittle material to a softer, more flexible one. Since polymers are generally unable to form films from latexes at temperatures below the Tg, an obvious requirement is that the polymer be above the Tg at the application and use temperature. A further restriction is placed on the Tg of the polymer by the fact that polymers become very soft at temperatures too far above the Tg, resulting in poor hardness, blocking, abrasion resistance, dirt collection, and so on. A balance must be obtained, therefore, between the good flexibility, adhesion, coalescence, and so forth, obtained at temperatures farther above the Tg and the good mechanical resistance properties found closer to the Tg. This is generally accomplished in coatings intended for ambient use by using polymers having Tg's in the 0°-30° C. range."

According the the above principle, Tg must be lower than the temperature at which film formation is attempted. If we choose the polymer with the lowest Tg of any described in the Stamicarbon patent, the composition is 60 parts by wt. bromostyrene (118° C. Tg), 15 parts acrylonitrile (110° C.), and 25 parts octyl acrylate (lowest Tg at -70° C. of esters of acrylic acid). The Tg of this composition is 43.7° C., according to the following equation: ##EQU1## Where Tg=multipolymer Tg in °K, Wn=weight fraction of the monomer present and Tg_(n) =the homopolymer Tg in °K.

The Tg of the above composition, 43.7° C., in the Stamicarbon's patent is recognized as too high to be of commercial value as a coating or a paint due to excessive stiffness and inability to form film properly at room temperature.

The Stamicarbon's compositions containing 60 to 95% bromostyrene, i.e., 26.2% Br to 41.5% Br, are outside those of the current invention (7-20% Br). Criteria for monomer selection include the glass transition temperature (Tg), physical properties, and chemical resistance. It is clear that the Stamicarbon's polymer composition cannot be such as recited by the present invention. Further, one skilled in the art would not utilize the latex of Stamicarbon as a coating or a paint to render articles nonflammable.

There has remained a need for polymer latices which possess desired flame retardant and film properties. It is also important that such latices be able to be conveniently blended with other latices in the same manner as flame retardants. The polymer latices of the present invention satisfy these needs, and are useful as fire retardant fabric backcoatings, coatings, paints, adhesives, sealants, caulking, non-woven binders and a variety of other applications.

SUMMARY OF THE INVENTION

In accordance with the present invention, there are provided polymer latices which comprise copolymers of ring-halogenated, ethylenically-unsaturated aromatic monomers and alkyl acrylate and/or methacrylate monomers, and which may also include at least one other monomer. In one aspect, the halogenated aromatic monomers are present in an amount to provide from 7 to 20 weight percent bromine in the final latex composition. In another aspect, the halogenated aromatic monomers include polybrominated monomers, particularly to provide monomers having an average of at least about 1.5 bromines per monomer unit.

The compositions of the present invention are exemplified by three categories of latex compositions. In a first embodiment, the latices include ring-brominated aromatic monomer units and second monomer units from alkyl acrylate monomer units, alkyl methacrylate monomer units, or combinations thereof. In a second embodiment, the latices include these first two types of monomer units and further include third monomer units selected from unsaturated esters of saturated carboxylic acids, halogen-free aromatic monomers or unsaturated carboxylic or dicarboxylic acid monomers. In a third embodiment, the latices include four monomer units, namely ring-brominated aromatic monomer units, alkyl acrylate and/or alkyl methacrylate monomer units, unsaturated carboxylic or dicarboxylic acid monomer units, and halogen-free aromatic monomers.

It is an object of the present invention to provide flame retardant polymer latex compositions which retain desirable physical properties.

A further object of the present invention is to provide flame retardant polymer latices which are useful for a wide variety of applications, including fabric backcoatings, coatings, paints, adhesives, sealants, caulking, non-woven binders and the like.

Further objects and advantages of the present invention will be apparent from the description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments described hereafter. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations, further modifications and applications of the principles of the invention as described herein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The present invention provides polymer latex compositions having advantageous physical properties making them useful for a wide variety of applications, and which latices have improved flame retardancy over prior art compositions. Past efforts have failed to provide compositions of the described type, while it has now been discovered that the inclusion of ring-brominated aromatic monomer units in polymer latices provides improved flame retardancy without deleterious affects on other physical attributes of the compositions.

The brominated aromatic monomers may generally be included in a variety of latex compositions, including but not limited to those in which non-brominated monomers have been known to be useful. The brominated monomers may be used in partial or total replacement of such non-brominated monomers. It is an aspect of the present invention that the described ring-brominated aromatic monomers may be used in the wide-ranging prior art compositions in which non-brominated aromatic monomers have been employed, with the consequent advantage being the achievement of improved flame retardancy without detrimental impact on the physical properties of the latex.

One, two or more monomers may be reacted with, for example, brominated styrene to produce the copolymer latices of the present invention. Careful selection of monomers used in conjunction with the brominated aromatic monomer enables production of flame retardant latices useful in a wide range of applications. These include textile backcoatings for woven upholstery and draperies, carpet backing, non-woven filter media binders, paints, adhesives, caulks, sealants and the like.

The copolymer latices of the present invention contain a ring-brominated aromatic monomer and at least one other monomer. The compositions of the present invention are exemplified by three categories of latex compositions. In a first embodiment, the latices include ring-brominated aromatic monomer units and units selected from alkyl acrylate monomer units, alkyl methacrylate monomer units or combinations thereof. In a second embodiment, the latices include these first two types of monomer units and further include third monomer units selected from unsaturated esters of saturated carboxylic acids, halogen-free aromatic monomers or unsaturated carboxylic or dicarboxylic acid monomers. In a third embodiment, the latices include four monomer units, namely ring-brominated aromatic monomer units, alkyl acrylate and/or alkyl methacrylate monomer units, unsaturated carboxylic or dicarboxylic acid monomer units, and halogen-free aromatic monomers.

The present invention employs ring-brominated aromatic monomer units of the formula (I): ##STR1## in which X=1 to 4, R₁ is --H or --CH₃, and R₂ is --H or an alkyl group having from 1 to 4 carbon atoms. Representative ring-halogenated aromatic monomers are styrene, methylstyrene, α-methylstyrene, α-methyl methylstyrene, ethylstyrene or α-methyl ethylstyrene with bromine substitution (mono, di, tri and tetra) in the phenyl nucleus. Mixtures or mixed isomers of the above monomers may also be used. As discussed more fully hereafter, the preferred ring-brominated aromatic monomer is polybrominated styrene, with dibromostyrene being most preferred. A preferred dibromostyrene material is one available from Great Lakes Chemical Corporation of West Lafayette, Ind., which material normally contains about 15 percent monobromostyrene and 3 percent tribromostyrene by weight.

In one aspect of the present invention, the ring-brominated aromatic monomer is included in the overall latex composition in an amount to provide sufficient bromine to yield the desired flame retardancy. In this respect, the ring-brominated monomer is included in an amount to provide from 7 to 20 percent bromine by weight of the overall composition. More preferably, the ring-brominated monomer is included in an amount to give from 9 to 18 percent bromine by weight.

In another aspect of the invention, it has been determined that it is preferable to utilize polybrominated forms of the ring-brominated aromatic monomer. This minimizes the number of ring-brominated monomer units required to achieve a given bromine weight percent of the overall composition. The use of a lower percentage of ring-brominated monomer units minimizes any adverse impact which such units would otherwise have on the physical properties of the latex. It is therefore an aspect of the present invention that the ring-brominated aromatic monomer units include polybrominated units, and that the ring-brominated monomer units include an average of at least about 1.5 bromines per unit. For latices containing monobrominated forms of the ring-brominated aromatic monomer units, it is preferred that at most about 20% of the ring-brominated aromatic monomer units be monobrominated.

At the same time, it is desirable that the latex compositions be readily prepared. Highly brominated, ethylenically-unsaturated, aromatic monomers, such as pure tetrabromostyrene, are not liquid at room temperature, and this interferes with the ready preparation of the latices. It is therefore preferred that the ratio of monobrominated and polybrominated monomer units in the latex be such that the corresponding mixture of the unsaturated ring-brominated aromatic monomers is liquid at room temperature. For example, a preferred material for use in the preparation of the latices of the present invention is the previously identified dibromostyrene composition as produced by Great Lakes Chemical Corporation, which composition is liquid at room temperature and comprises a mixture of 15 percent monobromostyrene, 82 percent dibromostyrene and 3 percent tribromostyrene. Other mono- and polybrominated aromatic monomer mixtures which are liquid at room temperature are similarly preferred for preparation of the present latex compositions. The mixtures preferably include as high an overall percentage of bromine as possible while still being a liquid at room temperature.

In a first embodiment of the present invention, the polymer latices contain the ring-brominated aromatic monomer units (I) and also include alkyl (meth)acrylate monomer units of the formula (II): ##STR2## in which R₁ is --H or --CH₃, and R₃ is an alkyl group of 1 to 20 carbon atoms. Representative alkyl acrylates useful in accordance with the present invention are methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, isohexyl acrylate, 2-ethylhexyl acrylate, n-heptyl acrylate, isoheptyl acrylate, 1-methyl-heptyl acrylate, n-octyl acrylate, isooctyl acrylates such as 6-methyl-heptyl acrylate, n-nonyl acrylate, isononyl acrylates such as 3,5,5-trimethylhexyl acrylate, n-decyl acrylate, lauryl acrylate and corresponding alkyl methacrylates and other primary, secondary and tertiary higher alkyl acrylates and methacrylates, where the alkyl radical can vary from 1 to 20 carbon atoms with the preferred species being those having 2 to 10 carbon atoms. The preferred monomers are ethyl acrylate, n-propyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate, and methyl methacrylate. In addition, the hydroxy alkyl esters of acrylic acid or methacrylic acid are useful in this invention.

In one aspect of the first embodiment of the present invention, the latex compositions comprise the ring-brominated aromatic monomer units and the alkyl acrylate and/or alkyl methacrylate monomer units. As discussed, the ring-brominated aromatic monomer units are preferably present in an amount to provide from 7 to 20 percent, and more preferably from 9 to 18 percent, bromine by weight of the overall composition. Also, the ring-brominated aromatic monomer units preferably include an average of at least about 1.5 bromines per unit. In another aspect of this first embodiment of the inventive latices, the composition consists essentially of the ring-brominated aromatic monomer units and the alkyl acrylate/methacrylate monomer units.

In a second embodiment of the present invention, the polymer latices include the ring-brominated aromatic monomer units (I) and the alkyl acrylate/methacrylate monomer units (II), and further include third monomer units of either unsaturated esters of saturated carboxylic acid monomer units (III), non-brominated aromatic monomer units (IV) or carboxylic or dicarboxylic acid monomer units (V).

The acid ester monomer units have the formula (III): ##STR3## in which R₄ is an alkyl group of 1 to 3 carbon atoms. Representative acid ester monomer units include vinyl acetate, vinyl propionate and vinyl butyrate, with vinyl acetate being preferred.

The non-brominated aromatic monomer units have the formula (IV): ##STR4## in which R₁ and R₂ are as previously defined. Typical halogen-free aromatic monomers are styrene, α-methylstyrene, methylstyrene, α-methyl methylstyrene, ethylstyrene and α-methyl ethylstyrene, with styrene or α-methylstyrene being preferred.

The carboxylic or dicarboxylic acid monomer units have the formula (V): ##STR5## in which R₁ is --H or --CH₃. Representative ethylenically unsaturated carboxylic acid monomers are acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. The preferred acids are acrylic and methacrylic acids.

Selection of the ring-brominated aromatic monomer units and the alkyl acrylate/methacrylate monomer units are as previously described. In a related aspect of the present invention, the latices consist essentially of the ring-brominated aromatic monomer units (I), the alkyl acrylate/methacrylate monomer units (II), and the third units selected from the group consisting of the acid ester monomer units (III), the non-brominated aromatic monomer units (IV) or the carboxylic or dicarboxylic acid monomer units (V).

In a third embodiment of the present invention, there are provided polymer latices including the ring-brominated aromatic monomer units (I), the alkyl acrylate/methacrylate monomer units (II), non-brominated aromatic monomer units (IV) and carboxylic or dicarboxylic acid monomer units (V). In a related aspect, the latices consist essentially of the ring-brominated aromatic monomer units (I), the alkyl acrylate/methacrylate monomer units (II), the non-brominated aromatic monomer units (IV) and the carboxylic or dicarboxylic acid monomer units (V).

Advantageously, the latices of the present invention may be prepared in accordance with conventional methods. For example, the latices are prepared by polymerizing in the emulsion system (water, emulsifier, initiator, and chain transfer agent) 100 parts by weight total monomers in the ratio desired in the polymer. Techniques for preparation of the latices include emulsion polymerization and dispersion of polymers prepared by solution, bulk or suspension polymerization. Suitable initiators include the initiators used for free radical polymerization such as organic peroxides, hydroperoxides, azo or diazo compounds, persulfates, redox systems, such as hydrogen peroxide-ferrous iron, persulfate redox systems, oil-soluble peroxygen compounds with ferrous iron, hydroperoxide-polyamine systems and others. Suitable emulsifiers include anionic, cationic, nonionic or amphoteric emulsifiers. Useful chain transfer agents include aliphatic, aryl mercaptans and disulfides, CCl₄, CBr₄, CHI₃ and CHCl₃, etc. Among these, mercaptans are preferred.

Polymerization may be carried out in the presence of air. Faster reactions are observed in the absence of oxygen at temperatures ranging from -30° to 110° C., with preferred temperatures ranging from about 0° C. to about 80° C.

The polymer latices of the present invention are useful as fire retardant fabric backcoatings, coatings, paints, adhesives, sealants, caulking, non-woven binders, etc. Monomer selection is based upon the final application of the latex. Criteria include the glass transition temperature (Tg), physical properties and chemical resistance desired.

The first factor to be taken into account in the choice of a monomer or monomer mixture is the glass transition temperature (Tg) of the polymer desired. This is the characteristic temperature at which the system undergoes a change from a hard, brittle material to a softer, more flexible one. Since polymers are generally unable to form films from latexes at temperatures below the Tg, a requirement is that the polymer be above the Tg at the application and use temperature. A further restriction is placed on the Tg of the polymer by the fact that polymers become very soft at temperatures too far above the Tg, resulting in poor hardness, blocking, abrasion resistance, dirt collection, and so on. A balance must be obtained, therefore, between the good flexibility adhesion, coalescence, and so forth, obtained at temperatures farther above the Tg and the good mechanical resistance properties found closer to the Tg. This is generally accomplished in coatings intended for ambient use by using polymers having Tg's in the -30° C. to 30° C. range, with preferred Tg's in the range of 0° C. to 30° C.

The flame retardant latices of the present invention may be admixed with other latex compositions, including non-flame retardant latices, to provide resulting latices and coatings having enhanced properties. In particular, the combination of the flame retardant latices used herein with other latices will yield coatings having improved flame retardancy. The latices of the present invention may then be provided with sufficient levels of bromine to yield the desired levels, such as previously indicated, for the resulting combined latices and coatings. Improvement in properties may also be achieved for such mixtures with respect to such aspects as adhesion, film forming, chemical resistance and flexibility.

The invention will be further described with reference to the following specific Examples. However, it will be understood that these Examples are illustrative and not restrictive in nature. Percents indicated are percents by weight unless indicated otherwise.

EXAMPLES 1-5 Preparation of DBS/2-EHA Copolymer Latices

A series of emulsion polymerizations of dibromostyrene (DBS)/2-ethylhexyl acrylate (2-EHA) were carried out in 8 oz. bottles. All the ingredients (122.50 or 180 parts by weight deionized water, 3 parts sodium dodecyl sulfate, 0.3 parts potassium persulfate, 0.2 parts t-dodecyl mercaptan and 100 parts total monomers in the ratio desired in the polymer) were charged into 8 oz. bottles and flushes well with nitrogen, and then reacted at 50° C. to about 45.8 or 36.5% solids in 15 hr. The whole bottle was cooled to room temperature and 3 parts deionized water and 0.18 parts 50% H₂ O₂ added, followed by agitation for 20 minutes. The results of these preparations are set forth in Table I. The latices in Examples 1 and 2 perform well in a variety of coating applications, and display improved flame retardancy, while the latices in Examples 3 through 5 give very soft and tacky coatings.

                  TABLE I                                                          ______________________________________                                         Preparation of DBS/2-EHA Copolymer Latices                                            Monomer                                                                        Charge     Reaction Solids                                                                               Conversion                                                                             Tg.sup.1                              Example                                                                               DBS/2-EHA  Time, hr %     %       °C.                            ______________________________________                                         1      34:66      15       45.8  100     -27.4                                 2      30:70      15       45.8  100     -33.4                                 3      20:80      15       45.8  100     -47.0                                 4      15:85      15       36.5  100     -53.2                                 5      12:88      15       36.5  100     -56.8                                 ______________________________________                                          .sup.1 Calculated Tg values according to the following equation:               ##STR6##                                                                      ?   where Tg=multipolymer Tg in °K, Wn=weight fraction of the            monomer present and Tg=the homopolymer Tg in °K (DBS, 414° K      and 2-EHA, 203° K)

Excellent latex compositions are similarly obtained by repetition of the foregoing methods with, for example, ethyl arylate, n-propyl acrylate and n-butyl acrylate.

EXAMPLES 6-11 Preparation of DBS/2-EHA/VAc Terpolymer Latices

The general procedure of Examples 1-5 was repeated to prepare terpolymer latices which contained 0-30 percent by weight of dibromostyrene (DBS), 15-80 percent by weight of 2-ethylhexyl acrylate (2-EHA) and 10-85 percent by weight of vinyl acetate (VAc). The reaction reached 95-100% conversion at 34.7-36.5% solids in 15-16.25 hr at 50° C., as shown in Table II. The latices in Examples 6 through 9 perform well in a variety of coating applications, and display improved flame retardancy while the latex in Example 10 gives very soft and tacky coating. The latex in Example 11 displays no flame retardancy. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the 2-ethylhexyl acrylate with ethyl acrylate, n-propyl acrylate, n-butyl acrylate and methyl methacrylate, and with replacement of the vinyl acetate with vinyl propionate and vinyl butyrate. The latices perform well in a variety of coating applications, and display improved flame retardancy.

                  TABLE II                                                         ______________________________________                                         Preparation of DBS/2-EHA/VAc Terpolymer Latices                                       Monomer                                                                        Charge                                                                         DBS/2-    Reaction Solids                                                                               Conversion                                                                             Tg.sup.1                               Example                                                                               EHA/VAc   Time, hr %     %       °C.                             ______________________________________                                         6      30:32:38  15       35.7  98      8.3                                    7      20:60:20  15       34.7  95      -29.0                                  8      20:40:40  15       35.7  98      -8.0                                   9      20:20:60  15       35.7  98      17.0                                   10     10:80:10    16.25  36.5  100     -51.4                                  11      0:15:85    16.25  35.9  98      9.2                                    ______________________________________                                          .sup.1 Calculated Tg values (DBS, 414° K.; 2EHA, 203° K. an      VAC, 303° K.)                                                     

EXAMPLES 12-17 Preparation of DBS/2-EHA/S Terpolymer Latices

The general procedure of Examples 1-5 was repeated to prepare terpolymer latices which contained 0-20 percent by weight of dibromostyrene (DBS), 10-60 percent by weight of 2-ethylhexyl acrylate (2-EHA) and 20-90 percent by weight of styrene (S). The monomers were polymerized to 91-100 percent conversion at 33.2-36.5 percent solids in 15-18.25 hr at 50° C., as indicated in Table III. The latices in Examples 12, 13, 15 and 16 perform well in a variety of coating applications, and display improved flame retardancy, while the latices in Examples 14 and 17 give excessively stiff coatings and form no film at room temperature. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the 2-ethylhexyl acrylate with ethyl acrylate, n-propyl acrylate, n-butyl acrylate and methyl methacrylate, and with replacement of the styrene with methylstyrene, α-methylstyrene, α-methyl methylstyrene, ethylstyrene and α-methyl ethylstyrene. The latices perform well in a variety of coating applications, and display improved flame retardancy.

                  TABLE III                                                        ______________________________________                                         Preparation of DBS/2-EHA/S Terpolymer Latices                                         Monomer                                                                        Charge                                                                         DBS/2-    Reaction Solids                                                                               Conversion                                                                             Tg.sup.3                               Example                                                                               EHA/S     Time, hr %     %       °C.                             ______________________________________                                         12     20:60:20  15.58    33.2  91      -21.4                                  13     20:40:40  15.58    36.5  100     10.6                                   14     20:20:60  15       35.5  97      52.0                                   15     15:40:45  18.25    36.1  99       9.6                                   16     10:40:50  18.25    36.1  99       8.5                                   17      0:10:90  18.25    36.1  99      71.2                                   ______________________________________                                          .sup.3 Calculated Tg values (DBS, 414° K.; 2EHA, 203° K. an      S, 373° K.)                                                       

EXAMPLES 18-24 Preparation of DBS/EA or BA/MAA Terpolymer Latices

Emulsion polymerizations of dibromostyrene (DBS)/ethyl acrylate (EA) or butyl acrylate (BA)/methacrylic acid (MAA) were carried out in 8 oz. bottles. The ingredients comprising 103.67 parts by weight deionized water, 3 parts sodium dodecyl sulfate, 0.3 parts potassium persulfate, 0.3 parts sodium bisulfite, with 0.2 parts or without t-dodecyl mercaptan, and 20-30 parts DBS, 0-80 parts EA or BA and 0-8 parts MAA were charged into 8 oz. bottles and flushed well with nitrogen, and then reacted at 50° C. to about 50% solids in 7 hr. The whole bottle was cooled to room temperature and neutralized with 1% NaOH to a pH of 7. The results of these preparations are set forth in Table IV. The latices in Examples 18 through 24 perform well in a variety of coating applications, and display improved flame retardancy. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the ethyl acrylate or butyl acrylate with n-propyl acrylate and 2-ethylhexyl acrylate, and with replacement of the methacrylic acid with acrylic acid, itaconic acid, maleic acid and fumaric acid. The latices perform well in a variety of coating applications, and display improved flame retardancy.

                  TABLE IV                                                         ______________________________________                                         Preparation of DBS/EA or BA/MAA Terpolymer Latices                                    Monomer                                                                        Charge                                                                         DBS/EA/   Reaction Solids                                                                               Conversion                                                                             Tg.sup.1                               Example                                                                               BA/MAA    Time, hr %     %       °C.                             ______________________________________                                         18     20:78:0:2 7        50    100       2.4                                  19     20:80:0:0 7        50    100      -0.5                                  20     30:0:67:3 7        50    100     -14.7                                  21     20:0:77:3 7        50    100     -28.6                                  22     20:0:76:4 7        50    100     -27.0                                  23     20:0:74:6 7        50    100     -23.8                                  24     20:0:72:8 7        50    100     -20.5                                  ______________________________________                                          .sup.1 Calculated Tg values (DBS, 414° K.; EA, 251° K.; BA,      217° K., and MAA, 501° K.)                                 

EXAMPLES 25-28 Preparation of DBS/2-EHA or EA/MMA Terpolymer Latices

The general procedure of Examples 18-24 was repeated to prepare terpolymer latices which contained 20-25 percent by weight of dibromostyrene (DBS), 0-65 percent by weight of 2-ethylhexyl acrylate (2-EHA) or ethyl acrylate (EA), and 15-23 percent by weight of methyl methacrylate (MMA). The reactions reached 100 percent conversion at 50% solids at 50° C. in 9 hr, as shown in Table V. The latices in Examples 25 through 28 perform well in a variety of coating applications, and display improved flame retardancy. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the 2-EHA or EA with n-propyl acrylate and butyl acrylate, and with replacement of the MMA with ethyl methacrylate, isopropyl methacrylate and t-butyl methacrylate. The latices perform well in a variety of coating applications, and display improved flame retardancy.

                  TABLE V                                                          ______________________________________                                         Preparation of DBS/2-EHA or EA/MMA Terpolymer Latices                                 Monomer                                                                        Charge                     Con-                                                DBS/2-EHA/  Reaction Solids                                                                               version                                                                               Tg.sup.1                              Example                                                                               EA/MMA      Time, hr %     %      °C.                            ______________________________________                                         25     20:65:0:15  9        50    100    -28.0                                 26     20:57:0:23  9        50    100    -16.6                                 27     25:0:57:18  9        50    100     25.4                                 28     20:0:57:23  9        50    100     24.4                                 ______________________________________                                          .sup.1 Calculated Tg values (DBS, 414° K.; 2EHA, 203° K.;        EA, 251° K., and MMA, 378° K.)                             

Preparation of DBS/EA/MMA/MAA Tetrapolymer Latices

Preparation of 0-20 percent dibromostyrene (DBS), 65 percent ethyl acrylate (EA), 13-33 percent methyl methacrylate (MMA) and 2 percent methacrylic acid (MAA) tetrapolymer latices was carried out in 8 oz. bottle by the same technique as described in Examples 1-5 except that 7.56 parts alkyl aryl polyether alcohol (Triton X-207 from Rohm & Haas, Philadelphia, Pa.) was dissolved in 100 parts total monomers and charged into the bottle containing 0.12 parts (NH₄)₂ S₂ O₈, 0.16 parts NaHSO₃ and 113.51 parts deionized water. The reactions reached 93-95 percent conversion at 45.3-46.3 percent solids at 65° C. in 2.5-4.5 hr, as shown in Table VI. The product was cooled to 30° C., strained, and the pH adjusted to 9.5 with 2-amino-2-methyl-1-propanol. The latex in Example 29 performs well in a variety of coating applications, displays improved flame retardancy, while the latex in Example 30 gives no flame retardancy. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the ethyl acrylate with 2-ethylhexyl acrylate, n-propyl acrylate and n-butyl acrylate, with replacement of the methyl methacrylate with ethyl methacrylate, isopropyl methacrylate and t-butyl methacrylate, and with replacement of the methacrylic acid with acrylic acid, itaconic acid, maleic acid and fumaric acid. The latices perform well in a variety of coating applications, and display improved flame retardancy, indicated by an oxygen index of 25.

                  TABLE VI                                                         ______________________________________                                         Preparation of DBS/EA/MMA/MAA Terpolymer Latices                                     Monomer                   Con-                                                 Charge                    ver-                                           Exam- DBS/EA/    Reaction Solids                                                                               sion Oxygen Tg.sup.1                           ple   MMA/MAA    Time. hr %     %    Index  °C.                         ______________________________________                                         29    20:65:13:2 4.5      45.3  93   25     16.3                               30     0:65:33:2 2.5      46.3  95   23     12.5                               ______________________________________                                          .sup.1 Calculated Tg values (DBS, 414° K.; EA, 251° K.; MMA      378° K., and MAA, 501° K.)                                 

EXAMPLES 31-34 Preparation of DBS/BA/S/MAA Tetrapolymer Latices

The general procedure of Examples 29-30 was repeated to prepare tetrapolymer latices which contained 0-30 percent by weight of dibromostyrene (DBS), 55-78 percent by weight of butyl acrylate (BA), 0-43 percent by weight of styrene (S) and 2-3 percent by weight of methacrylic acid (MAA). The reaction reached 94-97 percent conversion at 43.9-46.2 percent solids at 65° C. in 3.67-19.75 hr, as shown in Table VII. The product was cooled to 30° C., strained, and the pH adjusted to 9.5 with 2-amino-2-methyl-1-propanol. The latices in Examples 31 through 33 perform well in a variety of coating applications, and display improved flame retardancy, while the latex in Example 34 gives no flame retardancy. Similarly good latex compositions are obtained by repetition of the foregoing preparation with replacement of the butyl acrylate with ethyl acrylate, n-propyl acrylate and 2-ethylhexyl acrylate, with replacement of the styrene with methylstyrene, α-methylstyrene, α-methyl methylstyrene, ethylstyrene and α-methyl ethylstyrene, and with replacement of the methacrylic acid and acrylic acid, itaconic acid, maleic acid and fumaric acid. The latices perform well in a variety of coating applications, and display improved flame retardancy, indicated by an oxygen index of 24.

                  TABLE VII                                                        ______________________________________                                         Preparation of DBS/BA/S/MAA Tetrapolymer Latices                                     Monomer                  Con-                                                  Charge                   ver-                                            Exam- DBS/BA/   Reaction Solids                                                                               sion Oxygen Tg.sup.1                            ple   S/MAA     Time. hr %     %    Index  °C.                          ______________________________________                                         31    .sup. 30:67:0:3.sup.1                                                                    17       44.0  97   24     -14.7                               32    .sup. 20:78:0:2.sup.2                                                                       3.67  43.9  97   --     -30.1                               33     20:55:23:2                                                                                19.75  46.2  95   24      -0.8                               34     0:55:43:2                                                                               14       45.8  94   22      -4.7                               ______________________________________                                          .sup.1 Using 5 parts block copolymer of propylene oxide and ethylene oxid      (F108, BASF Wyandotte Corp., Parsippany, N.J.).                                .sup.2 Using 7.59 parts octylphenoxy polyethoxy ethanol (Triton X165, Roh      & Haas).                                                                       .sup.3 Calculated Tg values (DBS, 414° K.; BA, 217° K.; S,       373° K., and MAA, 501° K.)                                 

EXAMPLE 35 Preparation of Related Copolymer Latices

The preparation of related latex compositions as described previously yields equally advantageous products. For example, in place of dibromostyrene there is used a variety of ethylenically-unsaturated, ring-brominated aromatic monomers such as methylstyrene, α-methylstyrene, α-methyl methylstyrene, ethylstyrene and α-methyl ethylstyrene (with mono, di, tri and tetra bromine substitution in the benzene ring). In particular, brominated aromatic monomers including polybrominated units, and especially mixtures which are liquid at room temperature and have an average of at least 1.5 bromines per unit, permit ready preparation of the inventive latices, and yield compositions which have improved flame retardancy and good physical properties. Similarly, superior flame retardant latex compositions are obtained by preparations according to the earlier Examples with the use of alternate monomers as described previously in the text. The choice of monomers is primarily dependent on the physical properties desired for the resulting latices, and the presence of the ring-brominated aromatic monomer units provides increased flame retardancy for the products.

While the invention has been described in detail in the foregoing description and its specific Examples, the same is to be considered as illustrative and not restrictive in character. It is to be understood that only the preferred embodiments have been described, and that all changes and modifications that come within the spirit of the invention are desired to be protected. 

What is claimed is:
 1. A flame retardant polymer latex coating composition comprising ring-brominated aromatic monomer units of the formula (I): ##STR7## and alkyl (meth)acrylate monomer units of the formula (II): ##STR8## in which X=1 to 4, R₁ is --H or --CH₃, R₂ is --H or an alkyl group having from 1 to 4 carbon atoms, and R₃ is an alkyl group having from 1 to 20 carbon atoms, said ring-brominated aromatic monomer units including an average of at least about 1.5 bromines per unit, said flame retardant polymer latex coating composition having a glass transition temperature of between -33.4° C. and 25.4° C., and in which the ring-brominated aromatic monomer units are present in an amount to provide from 7 to 20 percent bromine by weight of the overall composition.
 2. The composition of claim 1 in which the ring-brominated aromatic monomer units include monobrominated units and polybrominated units, and in which no more than about 20% of the ring-brominated aromatic monomer units are monobrominated units.
 3. The composition of claim 1 in which the ratio of monobrominated and polybrominated units is such that the corresponding mixture of the unsaturated ring-brominated aromatic monomers is liquid at room temperature.
 4. The composition of claim 1 in which the ring-brominated monomer units are present in an amount to provide from about 9 weight percent bromine to about 18 weight percent bromine in the flame retardant polymer latex coating composition.
 5. The composition of claim 1 and consisting essentially of the ring-brominated aromatic monomer units and the alkyl (meth)acrylate monomer units.
 6. A flame retardant polymer latex coating composition comprising ring-brominated aromatic monomer units of the formula (I): ##STR9## and alkyl (meth)acrylate monomer units of the formula (II): ##STR10## and further comprising third monomer units selected from the group consisting of:(a) acid ester monomer units of the formula (III): ##STR11## (b) non-brominated aromatic monomer units of the formula (IV): ##STR12## and (c) carboxylic or dicarboxylic acid monomer units of the formula (V): ##STR13## in which X=1 to 4, R₁ is --H or --CH₃, R₂ is --H or an alkyl group having from 1 to 4 carbon atoms, and R₃ is an alkyl group having from 1 to 20 carbon atoms, and R₄ is an alkyl group having from 1 to 3 carbon atoms, said ring-brominated aromatic monomer units including an average of at least about 1.5 bromines per unit, said flame retardant polymer latex coating composition having a glass transition temperature of between -33.4° C. and 25.4° C., and in which the ring-brominated aromatic monomer units are present in an amount to provide from 7 to 20 percent bromine by weight of the overall composition.
 7. The composition of claim 6 and consisting essentially of the ring-brominated aromatic monomer units, the alkyl (meth)acrylate monomer units and the third monomer units selected from the group consisting of: (a) acid ester monomer units, (b) non-brominated aromatic monomer units and (c) carboxylic or dicarboxylic acid monomer units.
 8. The composition of claim 6 in which the ring-brominated monomer units are present in an amount to provide from 9 to 18 weight percent bromine.
 9. The composition of claim 6 in which the ratio of monobrominated and polybrominated units is such that the corresponding mixture of the unsaturated ring-brominated aromatic monomers is liquid at room temperature.
 10. The composition of claim 6 and consisting essentially of the ring-brominated aromatic monomer units, the alkyl (meth)acrylate monomer units and the third monomer units selected from the group consisting of: (a) acid ester monomer units, (b) non-brominated aromatic monomer units and (c) carboxylic or dicarboxylic acid monomer units.
 11. A flame retardant polymer latex coating composition comprising ring-brominated aromatic monomer units of the formula (I): ##STR14## and alkyl (meth)acrylate monomer units of the formula (II): ##STR15## non-brominated aromatic monomer units of the formula (IV): ##STR16## and carboxylic or dicarboxylic acid monomer units of the formula (V): ##STR17## in which X=1 to 4, R₁ is --H or --CH₃, R₂ is --H or an alkyl group having from 1 to 4 carbon atoms, and R₃ is an alkyl group having from 1 to 20 carbon atoms, said ring-brominated aromatic monomer units including an average of at least about 1.5 bromines per unit, said flame retardant polymer latex coating composition having a glass transition temperature of between -33.4° C. and 25.4° C., and in which the ring-brominated aromatic monomer units are present in an amount to provide from 7 to 20 percent bromine by weight of the overall composition.
 12. The composition of claim 11 in which the ring-brominated aromatic monomer units include monobrominated units and polybrominated units, and in which no more than about 20% of the ring-brominated aromatic monomer units are monobrominated units.
 13. The composition of claim 11 in which the ratio of monobrominated and polybrominated units is such that the corresponding mixture of the unsaturated ring-brominated aromatic monomers is liquid at room temperature.
 14. The composition of claim 11 and consisting essentially of the ring-brominated aromatic monomer units, the alkyl (meth)acrylate monomer units, the non-brominated aromatic monomer units and the carboxylic or dicarboxylic acid monomer units. 